Manufacturing method of polysilicon layer, and polysilicon thin film transistor and manufacturing method thereof

ABSTRACT

A manufacturing method of a polysilicon layer and a manufacturing method of a polysilicon thin film transistor. The manufacturing method of the polysilicon layer includes: providing a substrate; forming a barrier layer and a buffer layer on the substrate; disposing a plurality of grooves in the buffer layer by a patterning process, and forming crystal seeds on the buffer layer; forming an amorphous silicon layer on the buffer layer provided with the grooves and on the crystal seeds; transferring the amorphous silicon layer into a polysilicon layer using a thermal treatment process.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a manufacturing method ofa polysilicon layer, and a polysilicon thin film transistor and amanufacturing method thereof.

BACKGROUND

The existing displayers are mostly based on amorphous silicon (a-Si),i.e. the thin film transistors (TFT) on the display panels are mostlymade of amorphous silicon semiconductor materials. But in comparison,polysilicon (Poly-Si) has a higher electron mobility and has been deemedas a better TFT manufacturing method than amorphous silicon.

The current method of preparing a polysilicon TFT normally comprises:firstly preparing an amorphous silicon layer; transferring the amorphoussilicon layer into a polysilicon layer using an excimer laser annealing(ELA) method; and finally forming the thin film transistor according toconventional workflow. The inventor finds at least the followingproblems in the current method: more defects (e.g. grain boundarydefect, grain non-uniformity) in the process of forming the polysilicon,poor uniformity of the resultant polysilicon layer, and thus poorelectric performance and reliability of the polysilicon thin filmtransistor.

SUMMARY

Embodiments of the present invention provide a manufacturing method of apolysilicon layer, and a polysilicon thin film transistor and amanufacturing method thereof, wherein the polysilicon layer to be formedhas a high degree of crystallization, uniform grain and less grainboundary defect, so that the electric performance and reliability of thepolysilicon thin film transistor have been improved.

In order to solve the above technical problems, the embodiments of thepresent invention provide the following technical solutions:

A manufacturing method of a polysilicon layer, comprising:

providing a substrate;

forming a buffer layer on the substrate;

disposing a plurality of grooves in the buffer layer by a patterningprocess, and forming crystal seeds on the buffer layer;

forming an amorphous silicon layer on the buffer layer provided with thegrooves and on the crystal seeds;

transferring the amorphous silicon layer into a polysilicon layer usinga thermal treatment process.

In one example, the plurality of grooves is arranged respectively alonga first direction and a second direction intersecting the firstdirection to form an interleaved groove pattern.

In one example, at least one of the crystal seeds is arranged on thebuffer layer of a region surrounded by the adjacent grooves.

In one example, the step of disposing a plurality of grooves in thebuffer layer by patterning process and forming crystal seeds on thebuffer layer comprises:

forming a first amorphous silicon layer on the buffer layer;

transferring the first amorphous silicon layer into a first polysiliconlayer;

applying photoresist on the first polysilicon layer; after a multi-toneor half-tone exposure and development, forming aphotoresist-completely-removed first window region at a predeterminedposition where the grooves are subsequently formed, forming photoresistwith a second thickness at a predetermined position where the crystalseeds are subsequently formed, and forming photoresist with a firstthickness in other regions, the second thickness being greater than thefirst thickness;

etching to remove the first polysilicon layer and a part of the bufferlayer exposed from the first window region to form the grooves;

ashing to remove the photoresist with the first thickness;

etching to remove the first polysilicon layer to be exposed;

ashing to remove a remaining part of the photoresist with the secondthickness, to form the crystal seeds.

In one example, the first amorphous silicon layer has a thickness of10-20 nm.

In one example, the manufacturing method of the polysilicon layerfurther comprises:

passivating the polysilicon layer directly above the grooves in order toreduce grain boundary defects.

In one example, the step of passivating the polysilicon layer directlyabove the grooves in order to reduce grain boundary defects comprises:

applying photoresist on the polysilicon layer; after exposure anddevelopment, forming a photoresist-completely-removed second windowregion at a position corresponding to the grooves;

performing ion implantation to passivate the polysilicon layer exposedfrom the second window region;

removing the remaining photoresist.

In one example, the grooves have a width of 5-10 μm, and an intervalbetween the grooves is 10-20 μm.

In one example, the thermal treatment process is a solid phasecrystallization method or an excimer laser annealing method.

In one example, prior to forming the buffer layer, the method furthercomprises:

forming a barrier layer on the substrate.

In one example, after forming an amorphous silicon layer on the bufferlayer provided with the grooves and on the crystal seeds and prior totransferring the amorphous silicon layer into a polysilicon layer usinga thermal treatment process, the method further comprises:

performing annealing and surface treatment on the amorphous siliconlayer.

The embodiments of the present invention further provide a manufacturingmethod of a polysilicon thin film transistor, comprising forming apolysilicon layer using any of the aforementioned manufacturing methodsof the present invention, the polysilicon layer being used to form anactive layer of the polysilicon thin film transistor.

The embodiments of the present invention further provide a polysiliconthin film transistor, whose active layer is formed by the polysiliconlayer manufactured by the aforementioned manufacturing method ofpolysilicon layer.

The embodiments of the present invention further provide an arraysubstrate, comprising the aforementioned polysilicon thin filmtransistor.

The embodiments of the present invention further provide a displaydevice, comprising the aforementioned array substrate.

The embodiments of the present invention provide a manufacturing methodof a polysilicon layer, a manufacturing method of a polysilicon thinfilm transistor, a polysilicon thin film transistor manufactured by themethod in the embodiments, and an array substrate and a display deviceprovided with said polysilicon thin film transistor. The manufacturingmethod of the polysilicon layer pre-arranges grooves and crystal seedsin the buffer layer, and then forms an amorphous layer on the bufferlayer and transfers the amorphous silicon layer into a polysilicon layerusing a thermal treatment process. When the amorphous silicon is meltedand re-crystallized in the thermal treatment process, the grooves in thebuffer layer may provide extension space for the growth of the amorphoussilicon in a melted state so as to lower the height of grain boundary,while the crystal seeds may provide crystal nucleus for the growth ofthe amorphous silicon so as to speed up or promote the growth ofspecific crystal form. Therefore, the polysilicon formed by themanufacturing method of the embodiments of the present invention has ahigh degree of crystallization, uniform grain and less grain boundarydefect, so that the electric performance and reliability of thepolysilicon thin film transistor have been improved, and thus thereliability and display effect of the array substrate and the displaydevice have been improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to clearly illustrate the technical solution of the embodimentsof the invention, the illustrative drawings used for describing theembodiments will be briefly described in the following. It is obviousthat the described drawings are only related to some embodiments of theinvention and thus are not limitative of the invention.

FIG. 1 is a flow chart of a manufacturing method of the polysiliconlayer in an embodiment of the present invention;

FIGS. 2 (a)-(e) are respectively cross-sectional schematic views ofvarious film layers on a substrate in steps 11-15 of the manufacturingmethod of the polysilicon layer in the embodiment of the presentinvention;

FIG. 3 is a front top view of a buffer layer provided with grooves andthe crystal seeds thereon in the embodiment of the present invention;

FIG. 4 is a flow chart of forming the grooves and crystal seeds on thebuffer layer in step 103 in the embodiment of the present invention;

FIGS. 5 (a) and (b) are respectively cross-sectional schematic views ofthe film layers on the substrate after steps 1031 and 1032;

FIGS. 6 (a)-(e) are respectively cross-sectional schematic views of thefilm layers on the substrate after steps 1033-1037;

FIGS. 7 (a) and (b) are micrographs analyzing the surface of thepolysilicon manufactured by traditional method (a) and that by themethod in the embodiments of the present invention (b) by an atomicforce microscope (AFM);

FIG. 8 is a schematic view of step 106 performing interfacialpassivation on the polysilicon layer.

DETAILED DESCRIPTION

In order to make the object, technical solution and advantages of thepresent invention clearer, the technical solutions in the embodiments ofthe present invention will be described in a clearly and fullyunderstandable way in connection with the drawings related to theembodiments of the invention. Apparently, the described embodiments arejust a part but not all of the embodiments of the invention. Based onthe described embodiments herein, those skilled in the art can obtainother embodiment(s), without any inventive work, which should be withinthe scope of the invention.

Embodiments

The embodiments of the present invention provide a manufacturing methodof a polysilicon layer. As illustrated in FIGS. 1 and 2, the methodcomprises:

11. providing a substrate 100;

This step performs cleaning treatment on the substrate 100, and thesubstrate 100 may be a glass substrate or other substrates.

12. as illustrated in FIG. 2( b), sequentially forming a barrier layer110 and a buffer layer 120 on the substrate;

The barrier layer 110 is disposed between the substrate 100 and thebuffer layer 120, and may prevent the substrate 100 from being etched inthe subsequent step of forming grooves in the buffer layer 120. Inpractice, the buffer layer 120 may also be directly formed on thesubstrate 100, and the barrier layer 110 may be omitted.

Optionally, this step may continuously deposit the barrier layer 110 andthe buffer layer 120 on the substrate 100 using a plasma enhancedchemical vapor deposition (PECVD) method.

13. as illustrated in FIG. 2( c), disposing a plurality of grooves 121in the buffer layer 120 by a patterning process, and forming crystalseeds 132 on the buffer layer;

This step disposes a plurality of grooves 121 in the buffer layer 120,for providing extension space for the growth of the amorphous silicon ina melted state so as to lower the height of grain boundary upon theamorphous silicon being melted and re-crystallized; and it arrangescrystal seeds 132 on the surface of the buffer layer 120, for providingcrystal nucleus for the growth of the amorphous silicon so as to speedup or promote the growth of specific crystal form.

It may be determined according to the practical situations how todispose the grooves 121 in the buffer layer 120, how to arrange thegrooves 121, and the specific values of width d and interval L of thegrooves 121 and etc. Only one preferable embodiment will be described asan example hereinafter.

Preferably, as illustrated in FIG. 3, the plurality of grooves 121 inthe present embodiment is arranged respectively along a first direction(lateral direction) and a second direction (longitudinal direction)intersecting the first direction to form an interleaved groove pattern.Further preferably, at least one of the crystal seeds 132 is arranged onthe buffer layer of a region surrounded by the adjacent grooves 121. Tobe specific, in one preferable embodiment, a lattice region 20 issurrounded by two adjacent longitudinal grooves and two adjacent lateralgrooves, and one crystal seed 132 is disposed on the buffer layer ineach lattice region 20.

Optionally, the grooves have a width d of 5-10 μm, and an interval Lbetween the grooves is 10-20 μm.

To be specific, step 13 may dispose a plurality of grooves in the bufferlayer 120 by a patterning process and form crystal seeds 132 on thesurface of the buffer layer 120, as illustrated in FIG. 4, comprising:

131. forming a first amorphous layer 130 on the buffer layer 120;

In practice, as illustrated in FIG. 5( a), the plasma enhanced chemicalvapor deposition (PECVD) method may be used to continuously deposit thebarrier layer 110, the buffer layer 120 and the first amorphous siliconlayer 130 on the substrate 100, optionally, the first amorphous siliconlayer 130 has a thickness of 10-20 nm.

132. As illustrated in FIG. 5 (b), transferring the first amorphoussilicon layer 130 into a first polysilicon layer 131.

This step may adopt a Low Temperature Poly-Silicon (LTPS) technique toanneal and crystallize the first amorphous silicon layer 130, whereinthe crystallization process is preferably an excimer laser annealing(ELA) method, and may also be a solid phase crystallization method.

The following steps (133-137) are as illustrated in FIGS. 6 (a)-(e).

133. coating the first polysilicon layer 131 with photoresist 1311;after multi tone exposure and development, forming, aphotoresist-completely-removed first window region (region A) at apredetermined position where the grooves are subsequently formed,forming photoresist with a second thickness at a predetermined position(region B) where the crystal seeds are subsequently formed, and formingphotoresist with a first thickness in other regions (region C), thesecond thickness being greater than the first thickness;

The multi tone exposure in this step means the exposure using a MultiTone Mask (MTM) after coating with the photoresist. Since the lightintensities through different parts of the multi tone mask are differentfrom each other, the exposure intensities of corresponding parts of thephotoresist are different from each other, and photoresist patterns withdifferent thicknesses of photoresist may be obtained after development.

134. etching (i.e. the first etching) to remove the first polysiliconlayer 131 and a part of the buffer layer 120 exposed from the firstwindow region (region A) to form the grooves 121 of the buffer layer;

135. ashing to remove the photoresist with the first thickness;

Optionally, this step uses plasma to etch (ash) the photoresist toremove the photoresist of the photoresist region (B region) with thefirst thickness, and at the same time, the photoresist in the secondthickness corresponding region (B region) will also be thinned.

136. etching (i.e. the second etching) to remove the exposed firstpolysilicon layer 131;

This step removes the first polysilicon layer 131 in the first thicknessphotoresist corresponding region (C region) and keeps the polysiliconlayer in the photoresist covering region (B region) only.

137. ashing to remove the remaining photoresist in the second thicknesscorresponding region (B region) to form crystal seeds. In this case, thecrystal seeds 132 are distributed on the buffer layer 120. In apreferable embodiment, the grooves 121 and the crystal seeds 132 aredistributed on the buffer layer 120 as illustrated in FIG. 3, i.e. thegrooves 121 interleave each other to define a plurality of latticeregions 20, the buffer layer in each of which lattice regions 20 isprovided with a crystal seed 132, and preferably, the crystal seed 132is arranged at a central position of the lattice region 20.

14. as illustrated in FIG. 2 (d), forming an amorphous silicon layer 140on the buffer layer 120 provided with the grooves 121 and on the crystalseeds 132;

15. as illustrated in FIG. 2 (e), transferring the amorphous siliconlayer 140 into a polysilicon layer 141 using a thermal treatmentprocess.

Step 14 forms the amorphous silicon layer 140 on the buffer layer 120and the crystal seeds 132, and forms the second polysilicon layer 141using a thermal treatment process, as illustrated in FIG. 2 (e). What iscorresponding to the groove 121 of the buffer layer is an amorphoussilicon recess band 122. During the process of crystallization, thepolysilicon seeds (i.e. the crystal seeds 132) play the role of inducingre-growth of the silicon atom (indicated by the arrows in the figure),which may improve the crystallization efficiency. The grooves 121 of thebuffer layer have the effect of buffering during crystallization, i.e.providing extension space for the growth of the amorphous silicon, whicheffectively reduces grain boundary defects, lowers roughness of thepolysilicon surface and improves uniformity thereof.

FIG. 7 illustrates atomic force microscope (AFM) micrographs analyzingthe surface of the polysilicon manufactured by a traditional method (a)and that by the method in the embodiments of the present invention (b).Apparently, the polysilicon layer manufactured by the method in theembodiments of the present invention (b) has a significantly improvedsurface roughness and grain uniformity.

Further, the manufacturing method of a polysilicon layer in the presentembodiments further comprises:

16. passivating the polysilicon layer 120 directly above the grooves 121in order to reduce grain boundary defects.

To be specific, this step as illustrated in FIG. 8 comprises:

161. coating the polysilicon layer 141 with photoresist 150, forming,after exposure and development, a photoresist-completely-removed secondwindow region (region D) at a position corresponding to the grooves 121;

162. performing ion implantation to passivate the polysilicon layerexposed from the second window region (region D);

163. removing the remaining photoresist.

Steps 161-163 coats the polysilicon layer 120 with photoresist 150,forms the second window region corresponding to the grooves 121 of thebuffer layer by a strip patterning process, and then performing ionimplantation to form a grain boundary passivation region 123. Asillustrated in FIG. 8, the grain boundary passivation region is formeddirectly above the grooves 121 of the buffer layer.

After directional induced crystallization of the amorphous silicon instep 105, the grain boundary may be formed at a position correspondingto the grooves 121 of the buffer layer. Step 106 may directionallypassivate the grain boundary and form the passivation layer 123 by ionimplantation for controlling so as to reduce bad influence of grainboundary defects on the electric performance on the thin filmtransistor.

The embodiments of the present invention further provide a manufacturingmethod of a polysilicon thin film transistor, which differs from thetraditional polysilicon thin film transistor manufacturing method in theprocess of forming polysilicon at the front end. The polysilicon layeris formed using any of the aforementioned manufacturing methods in theembodiments, the polysilicon layer being used to form an active layer ofthe polysilicon thin film transistor.

The embodiments of the present invention introduce the crystal seeds,the grooves of buffer layer and the crystal boundary passivation regioninto the process of forming polysilicon at the front end, and theprocess of forming the thin film transistor is the same, which will notbe described in any more detail.

What needs to be pointed out is that the embodiments of the presentinvention may be used for manufacturing top gate (or bottom gate) typepolysilicon thin film transistor.

With the traditional excimer laser annealing technique, the grain sizeto be formed is not uniform, the polysilicon thin film has a poorroughness, the grain boundary defects have a high density, and the thinfilm transistor has poor electric performance and reliability. Theembodiments of the present invention make progress by introducing thecrystal seeds, the grooves of buffer layer and the crystal boundarypassivation region, which reduces the grain boundary defects and improvethe electric performance of the thin film transistor.

The embodiments of the present invention further provide a polysiliconthin film transistor, the process of manufacturing the polysilicon thinfilm transistor including forming the polysilicon layer using theaforementioned manufacturing method of polysilicon layer, thepolysilicon layer forming an active layer of the polysilicon thin filmtransistor.

Furthermore, the embodiments of the present invention provide an arraysubstrate, comprising the aforementioned polysilicon thin filmtransistor.

Furthermore, the embodiments of the present invention provide a displaydevice, comprising the aforementioned array substrate.

Although the embodiments of the present invention take the manufacturingof the polysilicon layer in LTPS back panel, it shall be understood thatthe application of the present invention is not limited to this, and theinvention may be adapted to all occasions requiring polysilicon filmlayer.

The above embodiments of the present invention are given by way ofillustration only and thus are not limitative of the protection scope ofthe present invention, which is determined by the attached claims.

What is claimed is:
 1. A manufacturing method of a polysilicon layer,comprising: providing a substrate; forming a buffer layer on thesubstrate; disposing a plurality of grooves in the buffer layer by apatterning process, and forming crystal seeds on the buffer layer,forming a first amorphous silicon layer on the buffer layer;transferring the first amorphous silicon layer into a first polysiliconlayer; applying photoresist on the first polysilicon layer; after amulti-tone or half-tone exposure and development, forming aphotoresist-completely-removed first window region at a predeterminedposition where the grooves are subsequently formed, forming photoresistwith a second thickness at a predetermined position where the crystalseeds are subsequently formed, and forming photoresist with a firstthickness in other regions, the second thickness being greater than thefirst thickness; etching to remove the first polysilicon layer and apart of the buffer layer exposed from the first window region to formthe grooves, ashing to remove the photoresist with the first thickness;etching to remove the first polysilicon layer to be exposed; ashing toremove a remaining part of the photoresist with the second thickness, toform the crystal seeds; wherein the plurality of grooves are arrangedrespectively along a first direction and a second direction intersectingthe first direction to form an interleaved groove pattern; forming anamorphous silicon layer on the buffer layer provided with the groovesand on the crystal seeds; transferring the amorphous silicon layer intoa polysilicon layer using a thermal treatment process.
 2. Themanufacturing method according to claim 1, wherein at least one of thecrystal seeds is arranged on the buffer layer of a region surrounded bythe adjacent grooves.
 3. The manufacturing method according to claim 1,wherein the first amorphous silicon layer has a thickness of 10-20 nm.4. The manufacturing method according to claim 1, further comprising:passivating the polysilicon layer directly above the grooves in order toreduce grain boundary defects.
 5. The manufacturing method according toclaim 4, wherein passivating the polysilicon layer directly above thegrooves in order to reduce grain boundary defects comprises: applyingphotoresist on the polysilicon layer; after exposure and development,forming a photoresist-completely-removed second window region at aposition corresponding to the grooves; performing ion implantation topassivate the polysilicon layer exposed from the second window region;removing the remaining photoresist.
 6. The manufacturing methodaccording to claim 1, wherein the grooves have a width of 5-10 μm, andan interval between the grooves is 10-20 μm.
 7. The manufacturing methodaccording to claim 1, wherein the thermal treatment process is a solidphase crystallization method or an excimer laser annealing method. 8.The manufacturing method according to claim 1, wherein prior to formingthe buffer layer, the method further comprises: forming a barrier layeron the substrate.
 9. The manufacturing method according to claim 1,wherein, after forming an amorphous silicon layer on the buffer layerprovided with the grooves and on the crystal seeds and prior totransferring the amorphous silicon layer into a polysilicon layer usinga thermal treatment process, the method further comprises: performingannealing and surface treatment on the amorphous silicon layer.
 10. Amanufacturing method of a polysilicon thin film transistor, comprisingforming a polysilicon layer, which is used to form an active layer ofthe polysilicon thin film transistor, wherein the polysilicon layer isformed by using the manufacturing methods according to claim
 1. 11. Apolysilicon thin film transistor, wherein an active layer of thepolysilicon thin film transistor is formed by the polysilicon layermanufactured by the manufacturing method according to claim
 1. 12. Themanufacturing method according to claim 2, wherein disposing a pluralityof grooves in the buffer layer by a patterning process and formingcrystal seeds on the buffer layer comprises: forming a first amorphoussilicon layer on the buffer layer; transferring the first amorphoussilicon layer into a first polysilicon layer; applying photoresist onthe first polysilicon layer; after a multi-tone or half-tone exposureand development, forming a photoresist-completely-removed first windowregion at a predetermined position where the grooves are subsequentlyformed, forming photoresist with a second thickness at a predeterminedposition where the crystal seeds are subsequently formed, and formingphotoresist with a first thickness in other regions, the secondthickness being greater than the first thickness; etching to remove thefirst polysilicon layer and a part of the buffer layer exposed from thefirst window region to form the grooves; ashing to remove thephotoresist with the first thickness; etching to remove the firstpolysilicon layer to be exposed; ashing to remove a remaining part ofthe photoresist with the second thickness, to form the crystal seeds.13. The manufacturing method according to claim 2, further comprising:passivating the polysilicon layer directly above the grooves in order toreduce grain boundary defects.
 14. The manufacturing method according toclaim 2, wherein the grooves have a width of 5-10 μm, and an intervalbetween the grooves is 10-20 μm.
 15. The manufacturing method accordingto claim 2, wherein the thermal treatment process is a solid phasecrystallization method or an excimer laser annealing method.